When Gordon Brown meets George Bush at Camp David today, we can be sure that he will not emulate his predecessor in wearing what the then British ambassador described as “ball-crushingly tight” trousers. The new prime minister does not do smart casual. There will probably be no jokes about the two men sharing a common interest in Colgate toothpaste. Mr Brown is determined to be businesslike. He also needs to demonstrate that he can do business with America.

To be fair to Mr Brown, his statement yesterday struck the right note on the relationship. It was, he said, Britain’s “single most important bilateral relationship” which he intended to make stronger. “We know we cannot solve any of the world’s major problems without the active engagement of the US,” he added. “And just as Britain and America have always stood side by side in tackling the great global challenges of the past, so we will continue to work very closely together as friends to tackle the great global challenges of the future.”

Warm words, which will be seen in Washing-ton as a welcome counterweight to the appointment of Lord Malloch Brown as a Foreign Office minister and a recent speech by Douglas Alexan-der, the international development secretary, which was widely interpreted as tilting away from America. These are challenging times for the special relationship and no more so than in the joint endeavours in Iraq and Afghanistan.

Two-thirds of Americans think the war in Iraq was a mistake and not worth the loss of more US lives. Mr Brown knows that the quicker he can get the troops out of Basra the happier the British public will be. Colonel H R McMaster, architect of the Baghdad “surge”, argues in our interview today that Iraq has become “a communal struggle incited by Al-Qaeda” that may last a generation. The best the allies can hope for is a retreat to acceptable levels of violence and Iraq’s armed forces being reliable enough to take the strain.

In Afghanistan the challenges are arguably greater. The army wants more troops and help from other Nato countries that have so far been lacking. Air Chief Marshal Sir Jock Stirrup, head of the armed forces, says significant progress has been made in Helmand province but in the big picture “it looks as if we’ve come hardly any distance”. Britain and America will be bound together in Afghanistan for years to come.

Mr Bush knows this and so does Mr Brown. Ahead of today’s visit the question for the political classes has been whether Britain should put more distance between itself and America. It is the wrong question. The real issue is whether Britain can help to persuade America not to distance herself from the rest of the world.

We take America’s international engagement for granted, forgetting it was not always this way. In the 1930s, alarmed by the shadow of war across Europe, Congress passed a series of neutrality acts. These and the activities of the America First Committee blocked US involvement in the second world war until Pearl Harbor.

Today, isolationist sentiment is on the rise again. Many in Congress see the outside world as a source of terrorism and the cheap goods that cost American jobs. One of Mr Bush’s more popular announcements was to develop biofuels as an alternative to US dependence on Middle Eastern oil. Ron Paul, an antiwar Republican, will not win his party’s presidential nomination but is doing better than expected. Hillary Clinton says that if she becomes president she will not waste time meeting foreign leaders hostile to America.

There are lessons to be learnt from the foreign policy mistakes made during the Bush era but a retreat into isolationism is not one of them. Mr Brown’s task today is to ensure a good working relationship with the man who will be in the White House for the next 18 months. Beyond that, he needs to help to ensure that the next occupant of the Oval Office is constructively engaged with the rest of the world.